What the fluff is this? - Gammarus pulex prefer food sources without plastic microfibers

Investigations into the impact of micro plastics (MP) and microfibers (MFs) upon the freshwater aquatic environment are still in their infancy despite our growing awareness of their importance. Gammarus pulex have long been used as a study organism for ecotoxicology and several studies have already used them to investigate the impact of MFs. One area of research which has not been exploited is the extent to which G. pulex can detect MFs and whether or not they avoid eating them. To answer this question we developed a reliable and accurate method of exposing Gammarus to known amounts of MF embedded in algal wafers. Here we show that when given the choice between control wafers and those contaminated with 2% or 3% MF Gammarus ingest fewer MF than would be expected if a random choice was made (2% W = 7 P = 0.01698, 3% W = 13 P = 0.03397). Their feeding behaviour also changes, with a significant reduction in time feeding (F_1,18 = 21.3 P = 0.0002) as well as significantly fewer visits to contaminated wafers (F_1,18 = 5.312 P = 0.0333). This suggests that G. pulex are able to detect MF in the 200-500 μm range and are partially repelled by them.